It has been conventionally known a reader which reads code symbols such as barcodes as an optical information reader which reads optical information on a reading target object by capturing an image of the reading target object through an imaging device and analyzing the image.
In the optical information reader as stated above, technologies described in NPL1 and PTL1 have been known as conventional technologies enabling reading of a barcode image which is difficult to read because of insufficient resolution by enhancing the resolution.
The technologies described in these documents are ones to obtain a high resolution image by using one-dimensional images of a plurality of lines each crossing a barcode area in a horizontal direction for a tilted barcode image and combining the images.
As illustrated in FIG. 19, gradations of a code symbol shown in one-dimensional images along two lines L1, L2 which cross a barcode area C have a lateral displacement D with a width of a non-integral multiple of a pixel pitch P depending on the tilt of the image, and the images may have information of resolution in the pixel pitch P or less. Accordingly, it is possible to enhance the resolution of the image by combining the images along the lines L1, L2.
Besides, in PTL2, it is described a technology in which a barcode is captured by an image sensor disposed under a state tilted for 45 degrees relative to a rectangular reading port, then two adjacent lines crossing the barcode which are in parallel with a diagonal line of the image are displaced for a half pitch from one another, so this displacement is utilized to obtain approximately double resolution by combining the lines relative to a case when one line is used.